This invention relates generally to borescopes or endoscopes of the type in which a video camera is mounted onto an elongated insertion tube which carries an image of a target that is concealed within an enclosure, i.e. the body cavity of a human patient. The invention is more particularly concerned with an add-on camera for an optical laparoscope which produces a video image of the target for display on a video monitor.
Recently, interest has increased in the use of video instruments for surgical applications to permit a surgeon to carry out a procedure with minimal intervention in the patient. An example of one such video instrument is a laparoscope for performing surgery in the abdominal cavity, where the instrument is inserted through a small incision. Other probes are provided for diagnosis of medical conditions in the colon or in the gastro-enteric tract. Small probes can also be used in eye surgery. Further examples are found in industrial probes, i.e., borescopes, for inspection of equipment such as boilers or steam generators, or of jet engine rotors where nondestructive penetration of the equipment is necessary.
Most commonly, a laparoscope employs a lens tube which acquires an image in an objective lens at its distal end, a relay lens system within the lens tube, and an ocular or eyepiece at the proximal end which permits viewing of tissues within the patient's body cavity.
In order to illuminate target body tissues, light is carried on optical fibers within the lens tube. A fitting at or near the proximal end of the lens tube contains one end of a fiber optic bundle, and couples to a flexible light conduit that in turn receives light from a light source. The fiber optic bundle fans out inside the lens tube and the fibers terminate at the distal or objective end.
A C-mount adapter is employed with a laparoscope to couple the eyepiece to a camera for observing the tissues on screen or for recording the image electronically or on film. The adapter has a fitting on its distal end for attaching to the laparoscope eyepiece, a standard malethread fitting on its proximal end for screw mounting to a camera, and a lens system for focusing and adjusting the image of the target.
Up until this time, camera attachments for optical laparoscope have been heavy and clumsy to use, and have require a separate light box for the illumination conduit and video processor and power supply for the camera. Also, up until now light sources for probes of this type have produced high levels of infrared, i.e., radiant heat, as well as visible radiation. The infrared causes a danger of tissue damage from heating. This limits the flexibility of laparoscopic procedures and limits the amount of time that any individual organ or tissue cluster can be observed.
Recently, a laparoscopic instrument has been proposed in which a small video camera is carried at the distal end of a rigid insertion tube, and a balanced white light is produced by a low-power metal halide discharge lamp which produces red, green, and blue visible light but only a minimal amount of infrared so that the danger of tissue damage is reduced. A device of this type is described in U.S. patent application Ser. No. 07/780,762, filed Oct. 22, 1991, and having a common assignee herewith.
In this type of instrument, the insertion tube is connected by a flexible cable or umbilical to a connector module that plugs into a socket in a light and power supply unit. A video cable that extends through the insertion tube and umbilical has terminals in the connector module that supply the video signal from the miniature camera to a wiring harness in the light and power supply unit, which supplies a suitable signal to a full color or monochrome monitor. An image of a target area, such as a tissue within an patient's body cavity, can be viewed on the monitor.
Also within the light and power supply unit is a high illuminance, but low-wattage light source in the form of one or more metal halide discharge lamps. These can preferably be of the type described in copending U.S. patent applications Ser. Nos. 07/484,166, filed Feb. 23, 1990; 07/636,742, 07/636,743, and 07/636,744, each filed Dec. 31, 1990, and which have an assignee common herewith. The lamp typically operates at a power of about 20 watts, and has an efficacy of 35 lumens per watt or more. The quality of light produced, which can be controlled by the selection of salts employed, the dosage of mercury, and mechanical structure, has an emission spectrum in the visible band, with very little radiation produced in the infrared band. Also, the arc gap of this lamp is small, which produces a small spot of light when focused onto the fiber optic bundle used for illumination. The small spot size allows almost all the light energy to be directed into the proximal end of a very small fiber bundle. The small illumination bundle permits the insertion tube to be made much smaller than was otherwise possible while still delivering plenty of light to the target area. Also, because small optical fiber bundles can be used, the probe can incorporate redundant optical fiber bundles which can each be associated with a respective light source. Moreover, because the lamp operates at low power (e.g. 20 watts), producing limited infrared radiation, and because virtually all the light is focused onto the fiber optic bundle, the light source can be made much more compact. Also, the lamp ballast and power supply can be made much smaller and easier to cool.
The light incident on the target contains substantially only visible light, with very little radiant heat. This permits the operator to view and examine tissues for extended intervals without danger of tissue damage.
The modular connector at the proximal end of the umbilical tube permits the instrument to be plugged into the socket of the light and power unit, or unplugged and then inserted in another similar unit as need be. Also, a number of instruments of similar or different styles, but with similar modular connectors, can be used interchangeably with one or another of the light and power units.
No one until now has made or proposed a video camera attachment for attaching to the eyepiece of a traditional optical laparoscope lens tube, and which can be quickly plugged into a light and power unit.